The present invention relates to a spindle motor for rotating an optical disc, magneto-optical disc or the like, and to a disc drive device that is provided with this spindle motor.
Disc drive devices equipped with head mechanisms for reading information recorded on a disc or writing information to a disc are known in the form of devices for optical discs such as CDs, DVDs and MDs, and for magneto-optical discs. As spindle motors used in such disc drive devices, external spindle motors, such as shown in FIG. 22, have been disclosed, for example in JP-2010-170632-A.
In the spindle motor 201 of FIG. 22, a disc supporting member (centering member) 203, which supports a disc 202 and is in contact with the inner edge of the center hole of the disc 202, is provided on the top face of a rotor holder (rotor case) 204. The disc supporting member 203 has a housing 203D comprising: a cylindrical portion 203A, which is fixed to the rotor holder 204; a planar portion 203B, which extends radially to the exterior from the bottom edge of the cylindrical portion 203A; and a guide 203C, which extends radially to the exterior from the planar portion 203B and guides the disc 202. A clamping magnet 206 and a back yoke 207 are disposed in the housing 203D. The clamping magnet 206 and the back yoke 207 serve to pull a magnetic body clamper 208, which is disposed on the top face of disc 202, toward the rotor holder.
In the spindle motor of FIG. 22, the back yoke 207 and the clamping magnet 206 are arranged stacked on the planar portion 203B of the disc supporting member 203; furthermore, with a view to reliably guiding the disc 202 by way of the guide 203C of the disc supporting member 203, it is common for the top edge of the guide 203C to be designed to be higher than the top face of the clamping magnet 206. Consequently, as the height from the top face of the rotor holder 204 to the top face of the clamping magnet 206 becomes greater, the height of the disc supporting member 203 becomes greater; the result is that the overall height of the spindle motor is greater.
Furthermore, when attempting to limit the height of the disc supporting member 203, the thickness of the clamping magnet 206 must be limited, but to limit the thickness while maintaining a prescribed attractive force, expensive magnets with a high magnetic flux density, such as rare earth magnets, must be used, and costs become higher.